Abstract 2886: KLF8 phosphorylation at Serine 48 by ERK2 is critical for its stability and function

Abstract

Krüppel-like factor 8 (KLF8) is a member of Krüppel like family transcription factor which was found to be upregulated in different types of cancers, primarily breast and ovarian cancer. It transcriptionally activates a host of downstream effectors like CyclinD1, EGFR, MMP9, and EPSTI1 to promote cell proliferation, cancer cell invasion and migration. Additionally, KLF8 transcriptionally represses E-cadherin to induce epithelial to mesenchymal transition and oncogenic transformation of cell. As such, KLF8 plays a central role in cancer progression. Several types of post-translational modifications including sumoylation, acetylation, ubiquitylation and PARylation have been discovered that regulate KLF8's function KLF8 has been shown to consistently migrate as doublet on SDS-PAGE. However, the reason for this motility shift of KLF8 has remained mysterious. We performed a series of experiments to determine the mechanism(s) behind this motility shift of KLF8. Truncation mutation showed that deletion of the first 50 amino acid residues, but not other regions, caused disappearance of the top band of the doublet, suggesting that the N50 region is responsible for the motility shift. Phosphatase treatment resulted in the same change in wild-type KLF8 protein, indicating that phosphorylation in the N50 region is causal to the motility shift. Further deletion and point mutation in this region identified Serine 48 as a novel phosphorylation site for KLF8. Interestingly, these experiments also identified KLF8 N terminal 31-40 region to play an important role in regulating the S48 phosphorylation and the motility shift. Our study identified that phosphorylation at Serine 48 is critical in maintaining KLF8 stability. Finally, we demonstrated that abolishing KLF8 S48 phosphorylation inhibits KLF8 mediated cancer cell migration. Kinase inhibitors treatment showed that ERK2 is the kinase responsible for KLF8 Serine 48 phosphorylation. Furthermore we identified that phosphorylated KLF8 acts as a mask to protect unphosphorylated KLF8. Overall this study identifies a novel phosphorylation site of KLF8 and a hitherto unknown link between ERK2 and KLF8 that is critical for maintaining its overall stability and function.

Citation Format: Satadru Lahiri, Heng Lu, Debarati Mukherjee, Lin Yu, Jihe Zhao. KLF8 phosphorylation at Serine 48 by ERK2 is critical for its stability and function. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2886.